Method of producing sheet-metal pipe



Patented Feb. 2, 1926'.

RICHARD IRVIN, 0F KNOXVILLE.. PENNSYLVANIA.

METHOD OF PRODUCING SHEET-METAL PIPE.

Application filedv December 21, 1922. Serial No. 608,306.

T0 all whom it may' concern:

Beit known that I, RICHARD IRVIN, residing at Knoxville, in the county of Allegheny and State of Pennsylvania., a citizen loi the United States, have invented or discovered certain new and useful Improvements in Methods of Producing Sheet-Metal Pipe, of which improvements the following is a specification.

My invention relates to sheet metal pipe, and its object is the production of `sheet metal pipe such in nature and character as to be applicable in a far wider range of utility than sheet metal pipe hitherto produced. l

Sheet metal pipe as hitherto produced is formed of sheet material, steel, copper, etc., rolled to proper gauge, cut, bent to cylindrical form, and completed by the interlock of the `'adjacent edges, or by soldering, or

`by both interlock and soldering. It is used for stove pipes, for rain-water conductors upon buildings, for speaking tubes, and for. various other purposes; but its use is limited, in that it is not'strong to withstand any con- 'siderable internal pressure,

I form thesheet-metal` pipe of my invention out of a material new for that urpose, namely, lead-clad steel, that is to say, sheet steel having a closely adherent surface of lead. I do not mean to limit my invention to particular-dimensions, but, by Way of example. in the ordinary practice of my invention I employ lead-clad steel sheets of 30 to 20 gauge having .on both sides coatings of commercially pure lead approximately two one-hundredths of an inch thick. The particular 'qualities and characteristics of this material, byy virtue of which I achieve [my invention and "produce a sheet metal pipe adapted for new uses, are the presence in one and the same sheet of the high tensile strength which the steel affords, the protection from corrosion yvhi'ch the lead coating affords, and-the possibilit-y of Welding at atmospheric temperature or substantially so, under pressure attainable in ordinary pipe-making methods;l 1

Lead-clad steel has4 not until recently beenv practically attained but latterly methods of production have been improved and lthat material is now produced commercially.

No sheet metal pipe has hitherto `been produced having a welded seam; the nearest approach has been a soldered seam, which of course is inferior vin strength. Such pressure as hitherto has been applied to the interlocked edges of the blank, in the course of sheet-metal pipe production, has been applied merely for the purpose of compressing und rendering mechanically more secure the seams so formed; never has any welding been attained. The materials IVhen the blank has been so assembled the seam is compressedl between an internally arranged mandrel 2 and an externally applied roll 3, with adequate-pressure, and the lead coatings which so are compressed surface upon surface are Welded one to another,

and so the seam is completed and secured,`

not by the mechanical strength arising from the mere interlocking of the edges of` a somewhat rigid blank, but from the adhesion of the components of the seam of sheet-metal pipe of ordinary construction` surface to surface.l The ordinary inturned and compressedseam is not integrated. but remains penetrable: the welded seam of my invention is a true integration and the joint is hermetically tight.

By 'such compression the double thickness of lead, which in the sea-m here illustrated is interposed between steel and steel at three points, a, b, and c, is by welding changed from six thin layers to three layers of double thickness integrated. with the steel, and so constituting an integrated joint throughout. The completed pipe is shown in Fig. II, and

lwill be understood without further'explanaftion.

No particular preparation of the material for this welding operation isrequired, beyond this, that .I am careful, as a metal worker should' be, to form my pi e out of the sheet material as it comes sh and clean from the mill.

I have said that I perform the welding at or substantially at atmospheric temperature. It will be understood that it may be performed at any temperature at which the hitherto used.b have been non-weldable at atmospheric tem? l welding of lead may under the available pressure be achieved, but necessarily the temperature will not exceed the melting point of lead.

The pressure which is present between mandrel and roller to effect welding is, in the operation as I have conducted it, at atmospheric temperature or substantially such, ap'

-proximately v1000 pounds. I give this ii ure merely by way of illustration, and onot intend to limit the invention thereby, but mean to 'over welding pressure generally, whatever be its actual value.

My-invention is achieved in the formation of the welded seam I have described. Imay,- and commonly do fortify and reenforce the seam so formed by runningsolder uon it. In this soldering I employ a'liquid ux compounded of cut acid (that is to say,a muriatic acid which has reacted .upon zinc until exhausted), a little turpentine, and a little salammoniac. ordinary solder of commerce, and the solder may be run onV with a soldering iron.

I proceed slowly with the soldering ogeration, to the end that the seam may e heated and that the solder may, therefore, penetrate deeply into 'the crevice and approach nearly the margin of the welded area.

' I find that, whereas the ordinary sheet metal pipe formed of tinned or alvanized lsteel may withstand aninterna pressure of 'not more than 2O pounds to the square ,mehr-beyond which point a higher pressure will -cause the seam to gape open, a

I use .thel

pipe otherwise similar, but formed of leadclad steel accordin to the method I have described, and wit out supplementary soldering, will withstand an lnternal pressure of 150' pounds, and if the supplementary soldering 'be resorted tothe pipe of my invention will withstand an internal pressure of 250 pounds, without gaping open. The joint of my invention in-its strength Ineasurably approaches the strength of the sheet material used, and not infrequently in my tests, the sheet itself has torn apart beforeV the welded seam has opened.

l Manifestly a sheet metal pipe strengthened to such degree becomes available kfor use in places to which ordinary sheet metal Y alsr without any addition of heat, other than that incident to the interloeked e ges.

In testimony Biol-IARD InvIN.4

ressure, welding together whereof I have hereunto set 

